1. Field of the Invention:
The present invention relates to a switching circuit and is mainly directed to an inverter circuit of an MIS integrated circuit, and has as an object providing a switching circuit which can improve the output voltage swing of an inverter without the need for two power sources.
2. Description of the Prior Art
In general, an inverter circuit of the MIS integrated circuit employs a MISFET as a load resistor and is classified into two types on the basis of the method of connection of a gate terminal, as illustrated in FIG. 1A and B. In this case, in the circuit in FIG. 1A, the load MISFET T.sub.L is used in a saturation mode in which the drain current does not depend on the drain voltage, while in the circuit in FIG. 1B, the load MISFET T.sub.L is used in a non-saturation mode in which the drain current depends on the drain voltage.
The swing of the output voltage of an inverter should desirably be large, and as between the two circuits, that in FIG. 1B is more advantageous in this respect. More specifically, in FIG. 1A, V.sub.DD = V.sub.GG, and the output level of the inverter circuit becomes V.sub.OL = V.sub.DD - V.sub.THL when driving MISFET T.sub.D is non-conductive, while in FIG. 1B, the output level of the inverter circuit becomes V.sub.OL = V.sub.DD by making the gate voltage of the load MISFET T.sub.L greater than the drain voltage (V.sub.GG &gt; V.sub.DD + V.sub.THL).
The inverter circuit in FIG. 1B, however, has had the disadvantage that two power sources are required for the inverter circuit since the gate voltage V.sub.GG of the load MISFET T.sub.L must be greater than the drain voltage thereof.